Implantable cardiac monitoring and/or stimulus systems are often designed to detect individual cardiac cycles or “beats.” It is common to design these systems to identify the R-wave or QRS complex of the cardiac signal. The R-wave or QRS complex can often be distinguished by virtue of being the largest amplitude signal. A “detection profile” can be used to detect events. Some illustrative examples of R-wave or QRS complex detection are shown in U.S. Pat. No. 5,709,215 to Perttu et al., and U.S. Pat. No. 8,565,878 to Allavatam et al., the disclosures of which are incorporated herein by reference.
Various difficulties with detection can arise, including variations in amplitude from one beat to the next and poor signal to noise ratio. These issues can cause overdetection of the cardiac signal, as may happen if both the R-wave and T-wave of a single cardiac cycle are incorrectly identified as being both R-waves of two separate cardiac cycles.